Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-04-17
2002-05-14
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S696000, C106S708000, C106S714000, C106S719000, C106S725000, C106S727000, C106S790000, C106S823000, C524S003000, C525S418000, C525S451000, C525S535000
Reexamination Certificate
active
06387176
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the priority of the European Patent Application No. 99 111 582.5 filed on Jun. 15, 1999, the disclosure of which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
The present invention concerns a multipurpose cement dispersing polymer, in particular a modified acrylic polymer.
BACKGROUND OF THE INVENTION
Concrete from ready mix plants or mixed on job sites, used in civil engineering constructions, e.g. anchorage of big bridges, base plates or side walls and box culverts, in building structures such as heavy reinforced structures, concrete filling pipe structures or other complicated structures, requires to be fully compacted to achieve its desired strength and durability. The existing and conventional method for compaction is by vibration of the freshly placed concrete.
A new production system for in situ-casted concrete is needed to improve significantly the cost situation as well as the health and safety aspects on the construction site.
Additionally, self-compacting concrete leads to a higher productivity, shorter building times and to an improved labor environment.
Increased fluidity (known as “slump” and slump-flow) can be effected by using large dosages of water in the concrete, but it is well known that the resulting cement-based structure. exhibits insufficient compactness and will have poor final compressive strength.
In order to avoid excess amount of water, flowing concrete can be produced by the addition of so called superplasticizers or high range water-reducing admixtures (HRWRs), like sulfonated melamine- or naphthalene-formaldehyde polycondensates or ligninsulfonate based admixtures. All of these well known polymers are not capable of causing the treated cement compositions to retain high flowability over a sustained period of time (known as “slump life”) without imparting a significant delay in the initial set time and considerable retardation of early strengths.
An additional disadvantage is the inconstant and very low flow rate of freshly prepared concrete of containing high quantities (e.g. 500 to 700 kgs/m
3
) of cement and up to 20% of silica fume and fly ash, which flow rate cannot be improved by the use of conventional HRWRs.
For heavy reinforced fresh precast concrete it is desired that the cementitious mixture has sufficient fluidity to flow through and around the reinforcement steel-structure to fill out the mold and level off at the top of the mold.
In the past ten years, various polymer-additives based on so-called polycarboxylic acid salts, e.g. copolymers of acrylic acid with acrylic esters of polyalkylene glycols have been proposed for imparting high water reduction, high flow and prolonged slump life to concrete, but most of them do not lead to self-compacting concrete without causing a too long retardation of the setting time and the early-strength development.
Enhancing early, i.e. 1 day, compressive strengths, is of high importance in the precast and prestressed concrete industry and chemical accelerators such as tertiary alkanolamines, alkali-and alkaline earthmetal thiocyanates, nitrites and halides are known in the art for this purpose and can be added separately to the fresh concrete.
Since calcium chloride and other inorganic salts can initiate corrosion of reinforcing steel embedded in hardened concrete, tertiary alkanolamines, which show both, accelerating and corrosion inhibiting properties are the most recommendable chemical accelerators.
Unfortunately, tertiary amines are well known to act as powerful catalysts for the cleavage of esters and from this reason can not be premixed with the acrylic ester polymers of the art and stored over longer periods, thus causing strongly reduced shelf life of the blend.
In order to improve the stability of such admixtures a deactivated form of alkanolamines was demanded which is reactivated in an alkaline environment.
With the introduction of a super high flow or self compacting concrete, which contains a multipurpose polymer simultaneously acting 1.) as a HRWR, 2) as set- and strength accelerator and 3) as corrosion inhibitor these problems could be solved, particularly the need for vibration can be significantly reduced.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a new category of multi-purpose polymers being capable to serve as a cement dispersing agent and which at the same time are set-accelerating and do have shrinkage reducing- and anticorrosive properties to steel. It was furthermore an objective to provide new cement dispersing, set-accelerating-, shrinkage reducing-, anti-corrosive admixtures for cement or mortar.
Said objectives are achieved by means of the modified acrylic polymers according to the main claim. Preferred embodiments are the object of dependent claims.
Surprisingly, it was found that the modified acrylic polymers according to the present invention do provide all the looked for properties, i.e. they could be employed as admixture for cement or mortar and could serve as a cement dispersing agent and at the same time are set-accelerating and do have shrinkage reducing- and anticorrosive properties to steel.
Said polymers according to the present invention are obtainable by reacting—in presence of a strongly acidic catalyst—1 mol of a poly(acrylic acid) A-1 or a C
1
-C
5
-ester thereof, having both a number average molecular weight of from 500 to 20,000
with 0.01-0.30 mol of a tertiary alkanolamine or a derivative thereof, represented by formula B-1
and, optionally with 0-0.80 mol of a monofunctional polyalkyleneglycol-monoalkylether, represented by formula D-1
HO—(CH
2
CHRO—)
x
R
3
D-1
and/or optionally with 0-0.60 mol of a &agr;-amino-polyalkyleneglycol-&ohgr;-alkylether of formula E-1
H
2
N—(CH
2
CHRO—)
y
R
3
E-1
wherein
each R independently represents a hydrogen atom or a methylgroup;
R
1
and R
2
independently represent a methyl group a hydroxyethyl(CH
2
CH
2
OH) group, an acetoxyethyl(CH
2
CH
2
OCOCH
3
) group, a hydroxy-isopropyl(CH
2
—CHOH—CH
3
) group, or an acetoxy-isopropyl(CH
2
—CHOCOCH
3
—CH
3
) group;
R
3
is a C
1
-C
4
-alkyl rest;
M represents hydrogen, a C
1
-C
5
-alkyl rest or an alkali metal ion, an alkaline earth metal ion or an ammonium group or a mixture thereof;
a is an integer of 5 to 270;
x and y independently represent integers from 2-250.
The modified acrylic polymers according to the present invention having an improved cement dispersing, set accelerating, early strength enhancing properties with shrinkage-reducing- and corrosion-inhibiting activity to steel, are preferably composed of at least three constituent units selected from the group given by formulas A, B, D and E:
wherein
each R independently represents a hydrogen atom or a methyl group;
R
1
and R
2
independently represent a methyl group, a hydroxyethyl(CH
2
CH
2
OH) group, an acetoxyethyl (CH
2
CH
2
OCOCH
3
) group, a hydroxy-isopropyl(CH
2
—CHOH—CH
3
) group, or an acetoxy-isopropyl(CH
2
—CHOCOCH
3
—CH
3
) group;
R
3
is a C
1
-C
4
alkyl rest,
M represents hydrogen, a C
1
-C
5
-alkyl rest or an alkali metal ion, an alkaline earth metal ion or an ammonium group or a mixture thereof;
m, n, p and q are numerical values representing the molarity of the constituent units A, B, D, B being present in the polymer, in a proportion of m:n:p:q=(0.1-0.8):(0.01-0.3):(0-0.8):(0-0.6), such, that m+n+p+q=a and p+q≠0;
x and y independently represent integers from 2-250.
The indices m, n, p and q indicate that respective numbers of monomer units are present in the polymer, whereby the monomer units are statistically distributed within the polymer.
The inventively found modified acrylic polymers are preferably obtained upon reacting the components A-1, B-1, D-1 and E-1 in presence of concentrated sulfuric acid as a catalyst and maintained at a temperature of about 140° to 180° C. for a period of from 2 to 8 hours.
In a preferred embodiment, the polyacrylic acid or its C
1
-C
4
alkyl ester has a number average molecu
Bürge Theodor A.
Krapf-Huber Anna
Sulser Ueli
Velten Ulf
Widmer Jörg
Burns Doane , Swecker, Mathis LLP
Green Anthony
Sika AG vorm. Kaspar Winkler & Co.
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